Description
The MK4 is a precision oriented upper receiver. Accuracy and consistency is the main focus here. No frills, just the most precision you can squeeze out of 5.56 AR platform without the price tag. I guarantee Sub MOA 5-shot groups with high quality ammo. In my personal testing I have gotten right at 1 MOA 10-shot groups. These are gassed to perform well with or without a suppressor. If you plan on using a lot of steel cased ammo we recommend Carbine Buffers and Springs. If you are running suppressed or only plan on using hotter ammo you may want to increase your buffer weight, again, depending on how you plan to run them. These are also not lightweight uppers as the barrels alone come in at just under 3lbs.
The Basics
18" SPR Ballistic Advantage 5.56 Barrel, 3 Choices of Handguards and Muzzle Devices, Toolcraft Chrome Lined BCG, and Mil-Spec Upper and Charging handle
The Specifics
Barrel:
Manufacturer - Ballistic Advantage SPR
Length/Chamber - 18" 5.56
Twist - 1:7 Twist
Material - 4150 Chrome Moly-Vanadium
Profile - SPR with OPS 12 Compatible Collar
Gas System - Rifle
Finish - Nitride
Thread Pitch - 1/2x28
Gas Port - Drilled to just above MK12 Spec .1065"
Dimpling - Double Dimpled (first time using a Dimpling Jig, Some of the dimplings are not pretty, but all of them are completely functional)
Weight - 41oz
1st Rebarrel - FREE
Barrel nut is sequentially torqued down to 50 FT-lbs. Starting at 25, then 35, and then finally 50 FT-lbs. to ensure proper mating of the threads.
If you legit burn out a barrel, like 10,000 -25,000 rounds, and the barrel becomes inaccurate I will rebarrel it for you for free. Good luck.
Bolt Carrier Group:
Manufacturer - Toolcraft
Bolt Material - C158 Tool Steel
Carrier Material - 8620 Alloy
Gas Key Material - 4130 Alloy
Profile - Full Auto
Finish - Phosphate With Chrome Lined Bore and Gas Key
Gas Key Screws - Grade 8 (torqued and staked to Mil-Spec)
Forward Assist Cuts
Mil-Spec Firing Pin (Hard Chrome Coated)
Toolcraft Description:
This Toolcraft Bolt is made of Mil-spec Carpenter 158 steel, shot peened, and mag particle inspected. Gas key is chrome lined, phosphate coated, and secured with grade 8 fasteners and staked per mil-spec. Full-auto bolt carrier is phosphate coated and chrome lined. Made in the USA.
Handguard: - 3 Options
Manufacturer - Aim Sports Wraith
Length - 13.5"
Material - 6061 T6 Aluminum
Finish - Hard Coat Black Anodization
Mounting Platform - 7-Sided Mlock
Barrel Nut - Steel (does not require timing)
Built in Anti-Rotation Tabs
Manufacturer - UTG PRO Quad (USA Made)
Length - 13"
Material - 6061 T6 Aluminum
Finish - Hard Coat Black Anodization
Mounting Platform - Quad Rails
Weight: 15.6 oz.
Pieces: 1
Rail Type: Picatinny/Weaver
No. of Rails: 4
Length: 12.6"
Width: 2.1"
Height: 2.4"
Manufacturer - UTG PRO Arwen (USA Made)
Length - 14"
Material - 6061 T6 Aluminum
Finish - Hard Coat Black Anodization
Mounting Platform - Mlock
Weight: 12.1 oz.
Width: 1.69"
Height: 2.07"
Upper Receiver:
Manufacturer - Anderson
Material - 7075 T6 Aluminum
Machined from Forged Aluminum
Finish - Type 3 Hardcoat Anodized Black
Standard Forward Assist
Standard Dust Cover
M4 Feed Ramps
NOT T-Marked, if you care...
Nothing special here, everything is Mil-Spec (standard), which is the way that I like it for an upper receiver.
Charging Handle:
Material - 7075 T6
Machined from Forged Aluminum
Finish - Type 3 Hardcoat Anodized + Teflon Coated for Smoother Operation
Same here, standard and boring. High quality, high strength, enough said.
Gas Block:
Material - Steel
Style - Low Profile
Size - .750"
Attachment Method - 2x Set Screws
Not Adjustable
You shouldn't really notice a good gas block and this one is no different. High quality steel that's as tough as the barrel for longevity. Rear set screw fits into the dimple on the barrel, ensuring proper alignment and that the gas block won't shift on you.
Set screws are torqued to 25 IN-lbs. and have High-Temp threadlocker applied for extra security.
Gas Tube:
Length - Rifle
Material - Stainless Steel
It's a stainless steel gas tube held in place with a roll pin, what more do you want?
Muzzle Devices
A2 Flash Hider - very basic flash hider
Strike Industries Venom - 4 Prong Flash Hider (great flash reduction, tuning fork sound)
Strike Industries King Comp - 2 Chamber Brake (goodbye recoil, goodbye neighbors)
